Electric linear motors are well known devices, in which one of a coil or magnet element is mounted to a fixed member, and the other element is mounted to a member to be moved. An electric current is applied to the coil, which generates magnetic lines of force to interact with the magnet to produce linear motion of the movable member. Such electric linear motors have been used in refrigeration compressors in which the movable member is the piston of the compressor and the magnet is mounted to said piston. The coil is fixedly mounted to an external portion of the compressor structure that forms the cylinder.
In a linear compressor of one known type, such as that shown in FIG. 1, the compression of the gas results from the axial movement of a piston 1 inside a cylinder 2 that has an external block 2a with an axial tubular wall 2b. The cylinder is closed by a cylinder head 3 on which there is a valve plate 3d on which are positioned a suction valve 3a and a discharge valve 3b. The valves regulate the inlet and outlet of the gas compressed in the cylinder. The piston is driven by an electric linear motor formed by a ring shaped actuator 4 that is attached to a base flange 1a of the piston. The actuator 4 supports a magnetic member 5, usually formed of permanent magnets. A coil 6 made of wire is fixedly mounted to the inner wall of a sleeve extension 6a of the cylinder 2. Electric current is supplied to the coil 6 to produce magnetic lines of force to interact with the permanent magnets and produce the linear reciprocating motion of the actuator 4 and the piston 1, with the magnet 5 moving between the outer wall of the sleeve extension 6a of the cylinder and the coil 6.
The piston 1 is mounted by means of a flexible rod 8 against a set of flat springs 7, and the set of flat springs 7 is rigidly mounted to the axial tubular wall 2b. The piston 1, actuator 4, magnetic component 5, flexible rod 8, and the set of flat springs 7 form together the resonant assembly of the compressor.
In the embodiment of FIG. 1, the set of flat springs against which the piston acts usually is made from spring steel plate. The flexible rod 8 has the function of reducing the forces resulting from mistakes in manufacturing of the component pieces and mistakes that occur during mounting, in order that such forces are not transmitted in their entirety to the piston, thereby avoiding wearing of the piston against the cylinder. Due to manufacturing asymmetries, the flat springs have a tendency to produce undesirable forces that are transverse to the flexible rod 8 and to the piston 1. Another problem of this construction is that the flat springs 7 are known to be relatively expensive to make, since they require sophisticated and complex cutting and finishing processes. The flexible rod 8 also is a component that is relatively difficult to make, since it has to be produced from special materials.
A second known embodiment of a linear compressor is shown in FIG. 2, in which a system of helical springs 20 substitutes the set of flat springs 7 of the prior art embodiment illustrated in FIG. 1. In this case, there is a first helical spring 20a mounted between the piston 1 and the cylinder 2, and a second helical spring 20b mounted between the piston and the bottom support wall 21 which is mounted to the axial tubular wall 2b. In this second embodiment of the prior art, the resonant assembly of the compressor is formed by the piston 1, actuator 4, magnet 5, and helical springs 20a, 20b. 
The construction of the compressor of FIG. 2 has the disadvantage of requiring a housing with relatively large dimensions to receive the helical springs 20a, 20b, each of the latter being positioned at each side of the base flange 1a of the piston. Further to the problem above, the momentum resulting from the eccentric force produced by the helical springs on the piston is not minimized or avoided, and this may produce wear of the moving component parts of the compressor.
As a function of the prior art problems mentioned above, a need exists for an improvement in the spring mounting system for a compressor of the type considered herein, that eliminates the disadvantages presently found.